Public health teams may no longer need to wait months to understand the toll of extreme heat, after new research suggested that near-real-time emergency department data can reveal health impacts while a heat wave is still unfolding.
Fast-moving data could change how heat risks are monitored
The study, published on August 31, 2026 in Nature Health, analyzed 8.1 million emergency department visits from summers between 2023 and 2025 across 19 Eastern U.S. states. Researchers from Harvard T.H. Chan School of Public Health and Boston University School of Public Health, working with Truveta, linked daily maximum temperatures to emergency visits for all causes, heat-related illness, kidney disease and psychiatric conditions.
According to the researchers, the approach offers a proof of concept for turning electronic health records into actionable intelligence during an ongoing climate event. They said the data could help health systems spot which groups are most affected, strengthen outreach, and adjust staffing before traditional claims-based data become available.
More than 13,000 excess emergency visits were tied to two heat waves
The analysis found that during the June 2025 heat wave, about 9.2% of all-cause emergency department visits were attributable to heat, equal to roughly 6,986 additional visits across the 19 states studied. During the August 2025 heat wave, about 8.3% of all-cause visits were attributable to heat, or about 6,351 additional visits.
Across both events, roughly 1 in 10 all-cause emergency visits on extreme heat days were linked to high temperatures. Nearly 30% of kidney disease-related visits during heat-wave periods were attributable to heat, while warmer temperatures were also associated with higher visit rates for psychiatric conditions.
Why researchers say the findings matter for public health planning
The research team said conventional heat-and-health studies often rely on insurance claims data that may arrive 6 to 18 months after an event, making it difficult to respond quickly. By contrast, the electronic health records used in this study were available within one week of the emergency department encounter.
Researchers said that kind of rapid surveillance could help local agencies decide where to open cooling centers, which communities may need stronger warnings, and whether interventions are working well enough to keep patients out of hospital during the same season.
The findings add to growing evidence that climate-related health threats need faster monitoring systems, especially as extreme heat becomes more frequent and severe. The study authors argued that timely data may prove essential for identifying risk and guiding interventions before the next heat event arrives.
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